Field of the Invention
The present invention relates to a pneumatic tire.
Description of the Related Art
With respect to pneumatic tires, there has been known a pneumatic tire provided with land portions defined by grooves formed on a surface of a tread. In such a pneumatic tire provided with such land portions, there may be a case where the land portion falls down due to a stress in a longitudinal direction or a lateral direction generated at the time of traveling or turning of a vehicle thus giving rise to uneven wear where the land portion locally wears.
In view of the above, in JP-A-2006-137231, to prevent a land portion defined by grooves from falling down, there has been proposed an idea of forming a plurality of projections on a side wall of the groove extending in a tire circumferential direction. However, in this literature, the projection is formed of a columnar portion projecting in a groove width direction and hence, rigidity of the projection is low whereby the falling-down land portion cannot be supported by the projections. Accordingly, there may be a case where uneven wear cannot be sufficiently suppressed.
In JP-A-3-86605, to efficiently drain water in the inside of a tire ground contact surface toward the outside of the ground contact surface at the time of high speed traveling, there has been proposed an idea where an inclined circumferential fin is formed on a side wall of a land portion defined by circumferential grooves and lateral grooves which faces the circumferential groove such that the circumferential fin projects from the side wall of the land portion from a position of a step-in side end portion of the land portion close to a tread surface to a position of a kick-out side end portion of the land portion close to a groove bottom of the circumferential groove. In JP-A-3-86605, if the circumferential fins formed on a pair of side walls which opposedly face each other with the circumferential groove sandwiched therebetween were brought into contact with each other, falling down of the land portion could be suppressed. However, the circumferential fins formed on the pair of side walls are inclined in the same direction and are arranged parallel to each other and hence, when the land portion falls down, one circumferential fin is sometimes positionally displaced upward or downward from the other circumferential fin whereby the circumferential fins are not brought into contact with each other thus giving rise to a case where falling down of the land portion cannot be suppressed until the circumferential fin is brought into contact with the side wall which opposedly faces the circumferential fin.
In JP-A-2010-30596, to improve the grounding property of a tire by realizing the uniform distribution of ground contact pressure of a land portion defined by main grooves extending in a tire circumferential direction and lateral grooves intersecting with main grooves, there has been proposed an idea of forming a projecting ridge which projects from a side surface of the land portion and continuously extends over the whole circumference of the side surface and forming the projecting ridge into a zigzag shape or a wave form having amplitude in a height direction of the land portion. However, the arrangement between the projecting ridge and a projecting ridge which is formed on an opposedly facing side wall with the main groove sandwiched therebetween is not taken into consideration. Accordingly, there may be a case where the projecting ridge is not brought into contact with the projecting ridge formed on the opposedly facing side wall so that falling down of the land portion cannot be suppressed until the projecting ridge is brought into contact with the side wall.